Adjustable pickup head for sound reproducing apparatus



APPARATUS Dec, 1, 1942.

R, 8. DAVIS Filed March 25, 1942 Patented Dec. 1, 1942 UNITED STATESADJUSTABLE PICKUP HEAD FOR SOUND REPRODUCING APPARATUS 4 Claims.

This invention relates to improvements in sound reproducing apparatusand particularly to r the manner ofmounting the pick-up head and itsneedle in the arm by which it is permitted to travel inwardly toward thecenter of the record disc in the usual phonograph.

The primary object of the invention is to provide means for moving thepick-up head and needle longitudinally of the arm in which they arecarried, as the arm and head swing inwardly of the disc, whereby therelationship of the needle and disc will remain substantially unchangedduring the playing of the record- More specifically, the inventioncontemplates an arrangement wherein the pick-up head and 15 its needleare slidably supported in the swingable arm and the head is connected bya link to lever pivoted on the arm eccentrically of the latter, saidlever being also connected by a second link to a fixed point, whereby,as the arm swings during the playing of a record, the lever will rock onits pivotal center and cause the pick-up head and needle tomove'longitudinally of the arm.

With these and other objects in view, the invention consists in certaindetails of construction and combinations and arrangements of parts, allas will hereinafter be more fully described and the novel featuresthereof particularly pointed out inthe appended claims.

In the accompanying drawing:

Figure 1 is a topplan view illustrating a record disc on the turntableof a phonograph and the pick-up head and arm in the relative positionsthey occupy when they are located adjacent the edge of the disc; Y.

Fig. 2 is a similar view illustrating the movement of the pick-up headwith respect to the disc and arm as the latter swings toward the centerof the disc; 7 V

Fig. 3 is a side elevation showing the arm and pick-up head more or lessdiagrammatically; and

Fig. 4 is a sectional view on the line 4-4 of Fi 3.

3 record disc I is shown on the turntable of the phonograph in Fig. 1,the turntable bein located somewhat above the upper surface H of thephonograph cabinet, as is well understood. Likewise, the arm 12,carrying the pick-up head l3 and needle i4, is pivoted at a suitablepoint on the surface I I, the arm being free to swing about its pivotalcenter toward the center of the disc in as the needle travels inwardlyof the disc by reason of its engagement'in the sound groove of saiddisc.

With the arm I: pivoted to swing around a cen- 5 larly attached to alever l8 pivoted at 19. Also arm 12 inwardly over the record will causethe tthe arm.- The path of the needle, during the PATENT OFFICE terfixed with respect to the record disc, the relationship of the needleand the surfaces of the sound groove would be changing constantly in theabsence of means for adjusting the relationship between the needle andarm, depending upon the location of the arm during the playing of arecord. To. eliminate this varying relationship of the needle and soundgroove, and the resultant effect on the sound reproduction, the presentinvention provides a comparatively simple arrangement wherein thepick-up is caused to slide lengthwise of arm l2 as the latter swingsinwardly over the record. For instance, the arm may be provided with anelongated vertical opening I5, with ways formed in the side walls ofsaid opening for reception of ribs IS on the pickup head, whereby thehead can slide longitudinally of the arm. 'One end of a link I! ispivotally attached to'the head and its opposite end is simipivotallyattached to said lever is one end of a second link 20, whose oppositeend is pivotally secured on a pin 2 l mounted on the upper surface ofthe cabinet in such fashion as to permit the arm to be raisedsufliciently to disengage the needle from the sound groove, as isnecessary at times. Preferably, the lever i8 is actually pivotedon thearm l2. a

By comparing the illustrations of Figs. 1 and 2, it will be seen thatthe swinging movement of links I! and 20 and lever l8 to tend to assumepositions in a straight line, thus causing the pickup head to be movedlongitudinally of the arm, away from the pin 2| and the pivotal centerof playing of the record, as affected by this movement of the headlongitudinally of the arm, is indicated at P in Fig. 2. Thus, the needleis maintained in substantially the same relationship with respect to thesound groove from the outer end to the inner end of that groove. Thatis, the needle is moved along the arm in a line which intersects thepivotal center of the arm and which is tangent to the point at which theneedle engages the sound groove in the record, and, as the needlemovesacross the record, the sliding movement of the pick-up head in the armwill always maintain the line of movement of the pick-up head coincidentwith lines tangential to the sound groove at the successive points ofengagement of the needle in said groove. In this way, both sides of thesound groove exert the same pressure on the needle because there is notendency on the part of the needle arm to pull the needle across thegroove. 7

To facilitate assembly 01' the head in arm I! in the specific form ofmounting illustrated, the end 22 of the arm may be made removable, beingdetachably secured in place on the arm by any suitable means, forinstance, screws 23.

What I claim is:

1. In a sound reproducing system comprising a pivoted swingable arm, apick-up head carried by said arm, and a sound groove engaging needle insaid head, said head being slidable longitudinally of the arm in a lineintersecting the pivotal center of the arm and tangent to the point atwhich said needle engages said groove, and means responsive to theswinging movement of the arm for-effecting a sliding movement of saidhead in said line.

2. In a sound reproducing system comprising a swingable arm, a supporton which said arm is pivoted, a pick-up head carried bysaid arm, and asound track engaging needle in said head, said head being slidable in aline intersecting the pivotal center of the arm and tangent to the pointat which said needle engages said track, a lever, a link connecting saidhead and lever, and means for rocking said lever upon swinging motion ofsaid arm to slide said head along said line.

3. In a sound reproducing system comprising a swingable arm, a supporton which said arm,

is pivoted, a pick-up head carried by said arm, and a sound trackengaging needle in said head, said head being slidable longitudinally oftheoarm in a line tangent to the point at which said needle engages thesound track and intersecting the pivotal center of the arm, a leverpivoted on said arm, the pivotal center of said lever being arrangedeccentrically of the pivotal center of the arm, means responsive to theswinging motion of the arm for rocking said lever, and a link pivotallyattached to said lever and pick-up head whereby said head is moved alongsaid line by the swinging movement of the arm.

4. In a sound reproducing system comprising a pivoted swingable arm, apick-up head, an a sound track engaging needle in said head, id headbeing slidably mounted in said arm or movement longitudinally of the armin a e intersecting the pivotal center of the arm and tangent to thepoint at which said needle engages said sound track, a lever carried bythe arm on a pivot arranged eccentrically of the pivotal center of thearm, a link pivotally connected to said head and one end 01' said lever,a support, and a second line pivotally attached to said sunport and theopposite end of said lever, whereby said lever will rock and slide saidpick-up along said line as the arm swings on its pivotal center.

RALPH B. DAVIS.

